Dual atrioventricular nodal non-reentrant tachycardia: Various atrioventricular conduction responses to atrioventricular simultaneous pacing

BACKGROUND Specific pacing methods to unmask the existence of the dual atrioventricular (AV) nodal pathway in patients with dual AV nodal non-reentrant tachycardia remain to be established.OBJECTIVE This study aimed to determine the electrophysiological characteristics of dual AV nodal non-reentrant tachycardia by its re-sponses to specific pacing methods.METHODS Five patients diagnosed as having dual AV nodal non -reentrant tachycardia were retrospectively investigated.RESULTS Atrial pacing could not induce the clinical tachycardia as continuous double firing in any of the 5 patients, but did induce sudden prolongation of the A-H interval as the linking phenomenon in 1 patient. A single atrial extrastimulation after sinus excitations was performed without interruption of double firing in 1 patient, and it induced the double ventricular response phenomenon within the limited range of the extrastimulus intervals. The pacing method of AV simultaneous basic pacing preceding atrial programmed extra -stimulation did not allow interruptions of double firing during the basic drive trains and induced the double ventricular response phe-nomenon within the limited range of the extrastimulus intervals in all 5 patients, even in 1 patient without inducibility of the clinical tachycardia in the catheterization laboratory. The double ventricu-lar response phenomenon within the limited range of the extrasti-mulus intervals may be based on the existence of the dual AV nodal pathway with concealed retrograde penetration.CONCLUSION The AV simultaneous basic pacing preceding atrial programmed extrastimulation method consistently and reproduc-ibly unmasked the existence of the dual AV nodal pathway as the double ventricular response phenomenon in patients with dual AV nodal non-reentrant tachycardia.